313 research outputs found
The End Magnets of the Ifusp Race-track Microtron Booster
The end magnets of the IFUSP race-track microtron booster, second stage of the electron accelerator under construction at the Linear Accelerator Laboratory, are presented. They deflect, focus and return the beam to the accelerating section. Details about the project are discussed, Poisson code was used to give the final geometry of the end magnets. The end magnets incorporate auxiliary pole pieces (clamps) which create a reverse fringe field region that avoids the beam vertical defocusing and reduces the horizontal displacement produced by extended fringe fields (EFF). The small gap height used for the clamps provided reverse field distributions with fringe fields of short extensions, avoiding the traditional use of inactive clamps. Measurements and calculations concerning particle trajectories and reverse field distribution are presented. The floating wire technique, employing an original procedure to register orbits, was used to corroborate the calculated beam trajectories and represents a good experimental option in the lack of the accelerator beam. The experimental results showed agreement of about 0.1% with the calculations
Geometry of River Networks II: Distributions of Component Size and Number
The structure of a river network may be seen as a discrete set of nested
sub-networks built out of individual stream segments. These network components
are assigned an integral stream order via a hierarchical and discrete ordering
method. Exponential relationships, known as Horton's laws, between stream order
and ensemble-averaged quantities pertaining to network components are observed.
We extend these observations to incorporate fluctuations and all higher moments
by developing functional relationships between distributions. The relationships
determined are drawn from a combination of theoretical analysis, analysis of
real river networks including the Mississippi, Amazon and Nile, and numerical
simulations on a model of directed, random networks. Underlying distributions
of stream segment lengths are identified as exponential. Combinations of these
distributions form single-humped distributions with exponential tails, the sums
of which are in turn shown to give power law distributions of stream lengths.
Distributions of basin area and stream segment frequency are also addressed.
The calculations identify a single length-scale as a measure of size
fluctuations in network components. This article is the second in a series of
three addressing the geometry of river networks.Comment: 16 pages, 13 figures, 4 tables, Revtex4, submitted to PR
Engaging patients and clinicians through simulation: rebalancing the dynamics of care
This paper proposes simulation-based enactment of care as an innovative and fruitful means of engaging patients and clinicians to create collaborative solutions to healthcare issues. This use of simulation is a radical departure from traditional transmission models of education and training. Instead, we frame simulation as co-development, through which professionals, patients and publics share their equally (though differently) expert perspectives. The paper argues that a process of participatory design can bring about new insights and that simulation offers understandings that cannot easily be expressed in words. Drawing on more than a decade of our groupâs research on simulation and engagement, the paper summarises findings from studies relating to clinician-patient collaboration and proposes a novel approach to address the current need. The paper outlines a mechanism whereby pathways of care are jointly created, shaped, tested and refined by professionals, patients, carers and others who are affected and concerned by clinical care
Combinations of Metarhizium anisopliae with chemical insecticides and their effectiveness in Mahanarva fimbriolata (Hemiptera: Cercopidae) control on sugarcane
Some insecticides can be used jointly with entomopathogenic fungi, and therefore the combi-
nation of chemical and biological control measures can be a safe and effective method to con-
trol insect pests. The aim of this study was to evaluate the costs and efficacy of combinations of
Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavicipitaceae) with thiameth-
oxam and imidacloprid on spittlebug (Mahanarva fimbriolata (StÄl); Hemiptera: Cercopidae)
control on sugarcane. The experiment was conducted as a randomized block design (RBD)
with 10 treatments and 4 replications. The treatments included a control (untreated), thia-
â1
â1
12
â1
methoxam (250 g ha ), imidacloprid (700 g ha ), M. anisopliae (M. a.) (3 Ă 10 conidia ha ),
A1 (3 Ă 10 12 M. a. conidia ha â1 + 65 g ha â1 of thiamethoxam), A2 (3 Ă 10 12 M. a. conidia ha â1 + 125
g ha â1 of thiamethoxam), A3 (3 Ă 10 12 M. a. conidia ha â1 + 187.5 g ha â1 of thiamethoxam), A4 (3 Ă
10 12 M. a. conidia ha â1 + 175 g ha â1 of imidacloprid), A5 (3 Ă 10 12 M. a. conidia ha â1 + 350 g ha â1 of
imidacloprid), and A6 (3 Ă 10 12 M. a. conidia ha â1 + 525g ha â1 of imidacloprid). The reductions
in the numbers of M. fimbriolata nymphs per treatment compared to the control were similar
at 15 DAT (days after treatment) in all treatments except combination A5 (M. anisopliae
and thiamethoxam). At 30 DAT, the numbers of nymphs were significantly reduced in all
treatments except A3, and their effectiveness ranged from 14.28% to 92.85%. At 45 DAT the
numbers of M. fimbriolata nymphs per treatment were significantly reduced in the following
treatments: imidacloprid alone at 700g ha -1 , A1, A2, A3, A4 and A6; and the combinations A1
and A2 caused the lowest M. fimbriolata nymph infestations and effectiveness rates of 77.41
and 87.09 %, respectively. At 75 DAT the 2 best control efficacies occurred in treatments A1 (3
Ă 10 12 M. a. conidia ha -1 of + 65g ha -1 of thiamethoxam) (82.1%) and A5 (78.6%) (3 Ă 10 12 M. a.
conidia ha â1 + 350 g ha â1 of imidacloprid). At 90 DAT the number of nymphs in the control had
increased 2.8 fold over the number at 75 DAT. Very good control efficacies at 90 DAT occurred
in all treatments with the combination of the fungus with an insecticide. At 105 DAT the
numbers of nymphs had surged in all treatments, and no treatment provided effective control.
The treatments with the highest earnings per hectare were A1 (3 Ă 10 12 M. a. conidia ha -1 + 65
g thiamethoxam) and M. anisopliae alone at the recommended dose of 3 Ă 10 12 M. a. conidia
ha -1 . Our findings demonstrate the effectiveness of using either thiamethoxam or imidacloprid
in combination with M. anisopliae to control M. fimbriolata nymphs on sugarcane, but greater
net earnings per hectare occurred with the lowest rate of the thiamethoxam combination than
with any of the imidacloprid combinations.Algunos insecticidas se puede utilizar con hongos entomopatĂłgenos y por lo tanto, la aso-
ciaciĂłn de los controles quĂmico y biolĂłgico puede ser una estrategia segura y eficaz para
el control de insectos-plaga. El objetivo de este estudio fue evaluar los costos y eficacia de combinaciones de Metarhizium anisopliae (Metschnikoff) Sorokin (Hypocreales: Clavi-
cipitaceae) con insecticidas thiamethoxam e imidacloprid para el control de la chicharrita
(Mahanarva fimbriolata (StĂ„l); Hemiptera: Cercopidae) en caña de azĂșcar . El experimento
fue conducido en un delineamiento en bloques casualizados (DBC), con 10 tratamientos y
4 repeticiones. Los tratamientos que incluidos el control (sin tratamiento), thiamethoxam
(250 g ha â1 ), imidacloprido (700 g ha â1 ), M. anisopliae (M.a.) (3Ă10 12 conidios ha â1 ), A1 (3Ă10 12
conidios ha â1 de M. a. + 65 g ha â1 de thiamethoxam), A2 (3Ă10 12 conidios ha â1 de M. a. + 125g
ha â1 de thiamethoxam), A3 (3Ă10 12 conidios ha â1 de M. a. + 187.5 g ha â1 de thiamethoxam), A4
(3Ă10 12 conidios ha â1 de M.a + 175 g ha â1 de imidacloprido), A5 (3Ă10 12 conidios ha â1 de M. a. +
350 g ha â1 de imidacloprido) y A6 (3Ă10 12 conidios ha â1 de M. a. + 525g ha â1 de imidacloprido).
Las reducciones en el nĂșmero de ninfas M. fimbriolata por tratamiento en comparaciĂłn con
el control fueron similares a los 15 DAT (dĂas pos tratamiento) en todos los tratamientos
excepto A5 combinaciĂłn (M. anisopliae y thiamethoxam). A los 30 DAT, el nĂșmero de ninfas
se redujeron significativamente en todos los tratamientos, excepto A3, y su eficacia variĂł de
14,28% para 92,85%. A los 45 DAT, los nĂșmeros de ninfas M. fimbriolata por tratamiento se
redujeron significativamente en los siguientes tratamientos: imidacloprido solo en 700 g ha -1 ,
A1, A2, A3, A4 y A6; y las combinaciones de A1 y A2 causaron la mĂĄs bajo infestaciones de
ninfas M. fimbriolata y sus tasas de eficacia fueron de 77,41 y 87,09%, respectivamente. A los
75 DAT, los 2 mejores eficacias de control se produjeron en tratamientos A1 (3Ă10 12 conidios
ha â1 de M. a. + 65 g ha â1 de thiamethoxam) y A5 (78.6%) (3Ă10 12 conidios ha â1 de M. a.+ 350
g ha â1 de imidacloprido). A los 90 DAT, el nĂșmero de ninfas en el control habĂa aumentado
2,8 veces mĂĄs el nĂșmero a 75 DAT. Muy buenas eficacias de control en 90 DAT, se produjo
en todos los tratamientos con la combinaciĂłn del hongo con un insecticida. A los 105 DAT, el
nĂșmero de ninfas habĂan aumentado en todos los tratamientos, y ningĂșn tratamiento habĂa
proporcionado un control efectivo. Los tratamientos con los mayores rendimientos hectĂĄrea
fueron A1 (3Ă10 12 conidios ha â1 de M. a.+ 65 g de thiamethoxam) y M. anisopliae solo a la dosis
recomendada de 3Ă10 12 conidios ha â1 de M. a. Nuestros resultados demuestran la eficacia de
thiamethoxam y imidacloprido en combinaciĂłn con M. anisopliae para el control de ninfas M.
fimbriolata en caña de azĂșcar, pero mayores beneficio neto por hectĂĄrea se produjeron con la
tasa mĂĄs baja de la combinaciĂłn de thiamethoxam que con cualquiera de las combinaciones
de imidacloprid
Blood flow changes using a 3D xenogeneic collagen matrix or a subepithelial connective tissue graft for root coverage procedures: a pilot study.
BACKGROUND: The study investigated the early healing process following the treatment of single Miller class I and II recessions with a 3D xenogeneic collagen matrix (CMX) or connective tissue graft (CTG). METHODS: This pilot investigation was designed as a single-center randomized controlled parallel trial. A total of eight subjects (four per group) were treated with either CMX or CTG in the anterior maxilla. Vascular flow changes were assessed by laser Doppler flowmetry (LDF) before and after surgery and at days 1, 2, 3, 7, 14, and 30 while clinical evaluations took place at baseline and at days 60 and 180. Pain intensity perception was evaluated by the short-form McGill pain questionnaire (SF-MPQ), at days 1 and 14. RESULTS: The vascular flow fluctuated similarly in both groups pre- and post-operatively, but the CTG exhibited a more homogeneous pattern as opposed to CMX that showed a second phase of increased blood flow at 14Â days. Clinically, the CTG led to greater change in mean root coverage and keratinized tissue gain but CMX was associated with lower early pain intensity scores. CONCLUSIONS: Within the limits of the study, the vascular flow alterations during the early healing of both graft types followed a similar pattern. The CMX was associated with a second peak of increased blood flow. CLINICAL RELEVANCE: The vascular flow changes after the application of CMX for single tooth recession root coverage did not show major differences from those observed after the use of a CTG. A trend for better clinical performance in terms of root coverage and keratinized tissue gain was noted for the CTG, but the initial patient morbidity was less for CMX
Involvement in teaching improves learning in medical students: a randomized cross-over study
<p>Abstract</p> <p>Background</p> <p>Peer-assisted learning has many purported benefits including preparing students as educators, improving communication skills and reducing faculty teaching burden. But comparatively little is known about the effects of teaching on learning outcomes of peer educators in medical education.</p> <p>Methods</p> <p>One hundred and thirty-five first year medical students were randomly allocated to 11 small groups for the Gastroenterology/Hematology Course at the University of Calgary. For each of 22 sessions, two students were randomly selected from each group to be peer educators. Students were surveyed to estimate time spent preparing as peer educator versus group member. Students completed an end-of-course 94 question multiple choice exam. A paired t-test was used to compare performance on clinical presentations for which students were peer educators to those for which they were not.</p> <p>Results</p> <p>Preparation time increased from a mean (SD) of 36 (33) minutes baseline to 99 (60) minutes when peer educators (Cohen's <it>d </it>= 1.3; p < 0.001). The mean score (SD) for clinical presentations in which students were peer educators was 80.7% (11.8) compared to77.6% (6.9) for those which they were not (<it>d </it>= 0.33; <it>p </it>< 0.01).</p> <p>Conclusion</p> <p>Our results suggest that involvement in teaching small group sessions improves medical students' knowledge acquisition and retention.</p
Sizing Up Allometric Scaling Theory
Metabolic rate, heart rate, lifespan, and many other physiological properties vary with body mass in systematic and interrelated ways. Present empirical data suggest that these scaling relationships take the form of power laws with exponents that are simple multiples of one quarter. A compelling explanation of this observation was put forward a decade ago by West, Brown, and Enquist (WBE). Their framework elucidates the link between metabolic rate and body mass by focusing on the dynamics and structure of resource distribution networksâthe cardiovascular system in the case of mammals. Within this framework the WBE model is based on eight assumptions from which it derives the well-known observed scaling exponent of 3/4. In this paper we clarify that this result only holds in the limit of infinite network size (body mass) and that the actual exponent predicted by the model depends on the sizes of the organisms being studied. Failure to clarify and to explore the nature of this approximation has led to debates about the WBE model that were at cross purposes. We compute analytical expressions for the finite-size corrections to the 3/4 exponent, resulting in a spectrum of scaling exponents as a function of absolute network size. When accounting for these corrections over a size range spanning the eight orders of magnitude observed in mammals, the WBE model predicts a scaling exponent of 0.81, seemingly at odds with data. We then proceed to study the sensitivity of the scaling exponent with respect to variations in several assumptions that underlie the WBE model, always in the context of finite-size corrections. Here too, the trends we derive from the model seem at odds with trends detectable in empirical data. Our work illustrates the utility of the WBE framework in reasoning about allometric scaling, while at the same time suggesting that the current canonical model may need amendments to bring its predictions fully in line with available datasets
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